Dynamic Modelling of Multiphase Machines Based on the VSD Transformation

Abstract

<div class="section abstract"><div class="htmlview paragraph">Multiphase machines continue to increase in popularity in high power applications due to their proven benefits compared to their three-phase counterparts. However, with the increased phase number and, therefore, the increased number of degrees of freedom, the complexity of both modelling and control strategies significantly increases. This paper proposes a dynamic modelling method for six-phase interior permanent magnet machines using the vector space decomposition transformation, which can be extended to machines with any number of phases. The proposed technique considers the nonlinear characteristics of the machine, such as spatial harmonics, magnetic saturation, and cross-coupling, which are based on flux linkage look-up tables from finite element analysis. The main contribution of this paper is the consideration of the effect of harmonic components and asymmetries within the machine windings on losses. These effects are mapped into a subspace orthogonal to the conventional <i>dq</i> subspace, which calls for additional transformations based on the field-oriented control structure. The proposed modelling strategy also allows for the inclusion of the high-frequency components generated from the switching instances from an inverter. The accuracy of the proposed model is validated through a comparison of the finite element analysis and Simulink torque waveforms and a comparison of Simulink and experimental current waveforms at low load operating conditions.</div></div>

Multiphase Traction Inverters: State-of-the-Art Review and Future Trends

“…A special case, however, is asymmetric MPIs with 3j, j ∈ [1, 2, ...] isolated neutrals. In such a configuration, all the vectors in 0 1 -0 2 are mapped at the origin, thus, nullifying the zero-sequence subspace [28]. Table 1 summarizes the harmonic mapping of the VSD transformation in the 2D orthogonal subspaces for five-, six-, seven-, and nine-phase MPIs.…”